Gas-Cushioned Aircraft Tie Rod for Severe Load Absorption
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Solution Overview
Problem
Existing tie rods in aircraft cabin monuments fail to effectively absorb severe loading events such as 9g forward inertia or rapid decompression, leading to potential failure and overstressing of joints, brackets, and panels.
Innovation Solution
A load absorbing tie rod with a pressurized gas cylinder that compresses during severe loading events, translating the piston to absorb and dampen loads, reducing stress concentrations and allowing monuments to displace, thereby minimizing load transfer to the aircraft structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional rigid tie rod is used to secure cabin interior monuments, then the structure provides strong support under normal loads, but it fails or over-stresses joints under severe loading events such as 9g forward inertia or rapid decompression
Solution Approach 1:
The tie rod system transitions from a static rigid connection to a dynamic system with a piston that can move relative to the outer cylinder. The piston is constrained by compressed gas under normal conditions but can translate during severe loading events, allowing the system to adapt its mechanical properties based on load conditions.
Solution Approach 2:
The system changes its mechanical parameter (stiffness) by transitioning from a locked state where the piston cannot move to an unlocked state where the piston can translate. This parameter change is triggered by load magnitude, with the compressed gas providing resistance at normal loads and allowing movement when loads exceed the gas pressure threshold.
2Reliability
If the tie rod is designed to withstand extreme loads of up to 25.0 kN, then reliability under severe loading improves, but the weight and structural requirements increase significantly
Solution Approach 1:
Compressed gas is pre-loaded into the system at a pressure between 9.9-19.7 MPa to provide beforehand cushioning against severe loading events. This pre-compressed gas acts as a cushion that absorbs extreme loads, allowing the use of lighter construction materials while maintaining reliability during 9g forward inertia or rapid decompression events.
Solution Approach 2:
The compressed gas acts as an intermediary between the piston and the external loading forces. Instead of directly transmitting extreme loads to the tie rod structure, the gas absorbs and dampens these forces, allowing lighter construction materials to be used while maintaining reliability during severe loading events.
3Stress or pressure
If a load-absorbing mechanism with piston and compressed gas is implemented, then stress concentrations and load transfer to aircraft structures are reduced, but the device complexity increases
Solution Approach 1:
The piston is nested within the outer cylinder, creating a compact integrated structure. The monument connector is coupled to the piston, and the aircraft connector is coupled to the outer cylinder, forming a nested arrangement that reduces space requirements while maintaining the load-absorbing functionality through the compressed gas mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The load absorbing tie rod reduces structural stress and weight requirements, enhancing safety and potentially lowering material costs by absorbing and dampening severe loads, thus allowing for lighter weight materials.
Implementation Method 1
a compressed gas located in a volume defined by the piston and the outer cylinder. The compressed gas is configured to allow translation of the piston toward a first end surface of the outer cylinder in response to a load greater than a first load threshold
Implementation Method 2
absorbing and damping severe loads, thus reducing structural strength requirements
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An aircraft assembly may comprise an interior aircraft monument, an aircraft structure, and a load absorbing tie rod coupled to the interior aircraft monument and the aircraft structure. The load absorbing tie rod may include an outer cylinder (126) coupled to the aircraft structure, a piston (128)located at least partially within the outer cylinder (126) and coupled to the interior aircraft monument, and a compressed gas located in a volume defined by the piston (128)and the outer cylinder (126).